310 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



chologists would now refer such a shell to the genus Natica, if it were to be 

 found among existing mollusks, 



This genus seems to be nearly, if not entirely, confined to the Cretaceous 

 rocks; though a few Tertiary species approach it more or less nearly in 

 general appearance. It occurs in both American and European Cretaceous 

 strata, as well as in those of Southern India. 



O y r o <1 e s Conradi, Meek. 

 Compare Natica (G-yrodes) crenata, Conrad (1860), Jour. Acad. Nat. Sci. Philad., IV, 289. 



Fig. 34. 



Fig. 33. 



Shell obliquely depressed-subglobose, 

 the height being about seven-eighths the 

 breadth ; volutions four to five, increasing 

 rapidly in size, the last one forming about 

 nine-tenths of the entire bulk, rounded on 

 the outer side, somewhat produced and 

 acutely carinated around the middle below, 

 and, like those of the spire, with the 

 truncation of the upper edge moderately 

 _ . _ .. broad and a little concave; spire much 



Gyroaes Conradi. L 



Fig. 33. View showing aperture and e a g e of depressed; umbilicus very broad and 

 nmbihcus. somewhat funnel-shaped, with its mar- 



Flg. 'M. An opposite side-view. ' 



Fig. 35. a view of the under side, showing ginal angle prominent, acute, and regularly 



the wide, open umbilicus, with its ... 



sharply carinate revolving margin. and rather distinctly crenate, while some 

 Fig. 30. An upper view of the same. distance within there is a second less 



prominent, linear, revolving ridge;* aperture subrhombic and about twice 

 as high as wide, distinctly angular at the termination of the revolving carina 

 of the under side of the body-volution below, and obtusely angular above; 

 outer lip very oblique, being produced above, and thence nearly straight, 

 and extending obliquely backward and downward to the basal angle, where 

 it connects with the lower extremity of the thin inner lip by a small, sharp 

 sinus, or emargi nation ; surface nearly smooth, or having obscure lines of 

 growth, that become stronger and show a tendency to gather into little 

 wrinkles on the upper truncated part of the volutions, while, on well- 

 preserved specimens, the faintest possible traces of tine, revolving striae may 

 be seen by the aid of a magnifier. 



* This inner angle, or ridge, is not seen in the figuro showing the under side, as it passes around 

 j ist at the margin of the dark rock tilling the deeper part of the umbilicus. 



